An automobile with three voltage power supply system and control method

The present invention relates to a power supply for the car, particularly a car with three voltage power supply system and control method. The system includes a 12V power supply unit, 48V power supply unit, 300V power supply unit, DC / DC converter Z1, DC / DC converter Z2; DC wherein the DC / DC converter Z1 and the low pressure side of the power supply unit 12V 12V power supply connection, the high voltage terminal and 48V power supply unit connected to the 48V power source; said DC / DC converter and the low pressure side Z2 48V power source connected to the high voltage terminal connected to the 300V power supply unit 300V power supply; third voltage supply control system the method comprises preheating step at a low temperature power, charge and discharge control based on the SOC of power. The present invention overcomes the car interior is a low voltage power supply circuit current is too large, easily lead to larger matching engine fuel consumption rate is too high and cold regions lithium-ion battery discharge difficult problems automobiles with three voltage power supply and control method.